Orthodontic treatment with the contemporary fixed appliance phase I: Laying the foundation, diagnostics and precise appliance placement

Introduction

Comprehensive orthodontic treatment typically involves the use of contemporary fixed appliance (CFA) therapy. This process follows a standardised protocol, although variations in implementation can occur due to individual case differences. ^, A critical aspect of orthodontic planning involves determining the anchorage requirements, which can influence the choice of armamentarium and appliance, including molar tubes, auxiliary appliances and integration of mini screw implants (MSI) or skeletal anchorage systems (SAS). This chapter outlines the step-by-step sequence of events involved in an orthodontic consultation and the process of implementing orthodontic appliances in the mouth.

First appointment and records

During the first interaction with the patient and their family, a relaxed and friendly meeting is conducted in a room that is not a typical dental clinic setting ( Fig. 54.1 ). The primary purpose of this meeting is to gather important information such as the concerns of parents and patients, any medical and dental history that might limit or contraindicate orthodontic treatment, the motivation for seeking orthodontic treatment, the patient and parents’ expectations on aesthetic and functional benefits, the commitment to dental/orthodontic treatment, social and economic status, and the overall personality of the patient.

Image, AltText currently not available — Figure 54.1

Before the first appointment with an orthodontist, the patient and their parents may receive an information brochure on orthodontic treatment or be directed to the doctor’s website by the secretary. During this first interaction, a detailed history and clinical examination may be recorded and, if possible, the first case records can be prepared.

Essential diagnostic records include upper and lower study models and clinical photographs consisting of five extraoral and five intraoral views. Although a lateral cephalogram and orthopantomogram (OPG) are crucial, many clinicians only undertake on these records if clinical situations warrant them. Posteroanterior (PA) cephalograms and radiographs of the temporomandibular joints (TMJ) may be obtained if indicated. Some clinicians prefer to complete the records in more than one sitting, with non-X-ray records in the first appointment and X-ray-related records in the second to avoid patient fatigue.

Designing a treatment plan and execution strategy

Orthodontic treatment is a process that must be approached in a way that considers the patient’s oral and general health, intending to address their concerns. As part of this process, the patient and their guardian must be informed about each treatment phase, including retention and follow-up. They should also be made aware of the need for compliance and commitment and any limitations on treatment outcomes that may arise due to dental or medical conditions. Additionally, the cost and financial aspects of the treatment should be clearly defined and agreed upon ahead of time ( Fig. 54.2 ).

To reduce the burden of care, the number of visits for orthodontic treatment should be minimised. Oral health education and prevention of dental diseases should be reinforced during and before treatment. Emphasis should be given to plaque control and eating habits, and regular dental recall visits should continue with the family dentist.

Orthodontic treatment aims to achieve the best possible results for each patient based on their needs. The treatment plan should be feasible and practical and must be discussed and agreed upon by both the patient and the orthodontist before beginning any treatment.

The treatment outcome should optimise periodontal and dental conditions, arch form and occlusion while minimising risks such as gingival recession, loss of supporting bone, root resorption, dental caries or tooth decalcification. The patient and their parents should be educated about possible undesirable treatment effects likely to be observed during or after treatment and modalities to avoid or minimise them.

The post-treatment outcome should be envisaged based on the severity and complexity of the malocclusion and the feasible delivery of the treatment. The clinical observations, history, growth analysis and information derived from diagnostic cast measurements and cephalometric analysis are used to formulate a formal problem list, and the goals of treatment are outlined.

Treatment planning is a crucial stage in orthodontic treatment. It involves identifying the problems that must be addressed, determining appropriate treatment modalities, devising treatment strategies and considering the biomechanics engaged at each step.

At this stage, the retention plan is also considered, and factors such as the retention duration, possible prognosis and expected treatment outcomes are carefully thought through.

The planned treatment approach is discussed in detail with the patient and their parents. They are provided with a comprehensive explanation of all possible steps and consequences of orthodontic treatment, including any potential risks. This helps them make an informed decision about whether to proceed with the treatment.

Planning anchorage and appliances for enhancing anchorage

Anchorage is the most critical aspect of orthodontics. Much of the biomechanics of treatment planning revolves around estimating anchorage requirements and thoughtfully selecting appliances or effective anchorage control.

Need for anchorage

Force is the active ingredient of the appliance, the only drug in orthodontics. An orthodontic appliance consists of an active member and a reactive member. The active member generates force to initiate and conduct tooth movement. The active components are housed in the body of the appliance, which is secured in the mouth through an ‘anchor unit’.

In 1923, Louis Ottofy defined anchorage as the ‘base against which orthodontic force or reaction of orthodontic force is applied’.

Most recently, Daskalogiannakis defined anchorage as ‘resistance to unwanted tooth movement’. Graber defined anchorage in orthodontics as the ‘nature and degree of resistance to displacement offered by an anatomic unit when used for the purpose of effecting tooth movement’.

Classification of anchorage requirements

Gianelly and Goldman suggested the terms maximum, moderate and minimum to indicate the extent to which the teeth of the active and reactive units should move when a force is applied.

Nanda classified anchorage into three categories: A, B and C, depending on how much of the anchorage unit contributes to extraction space closure ( Fig. 54.3 ).

•
Group A space closure includes 75%–100% space closure from anterior retraction and 25% closure from posterior anchorage movement. There is a critical posterior anchorage.
•
Group B space closure includes an equal amount of anterior and posterior tooth movement to close the space.
•
Group C space closure includes 75%–100% posterior protraction. There is a critical anterior anchorage and a non-critical posterior anchorage.

The introduction of skeletal anchorage systems (SAS) and temporary anchorage devices (TADs) to the orthodontic armamentarium makes 100% anchorage conservation a reality. Hence, group D is added as an additional category, whereby all the extraction space can be utilised for retraction of the anterior segment.

Factors affecting anchorage requirements

Conventionally, the anterior segment must be retracted to close the space created by the extraction of the first premolars. The premolar extraction spaces are closed using buccal segments as anchor teeth.

Nature of malocclusion

Anchorage demands depend upon several factors, such as the nature and complexity of malocclusion, total arch length discrepancy (TALD), growth pattern, the type of tooth/teeth movements required, the individual’s craniofacial pattern and age. The total discrepancy is based on the sum of crowding, the necessary amount of retraction and the space required to level the curve of Spee. A high discrepancy demands maximum anchorage to close extraction spaces. Crowding cases demand maximum anchorage control during the initial stages of levelling and alignment. On the other hand, increased overjet and protruded dentition, as in bimaxillary cases, demand maximum retraction and, therefore, high anchorage during retraction.

Craniofacial pattern

Given the same amount of discrepancy and type of malocclusion, the variance in an individual’s craniofacial pattern would influence the anchorage offered by the anchorage units. The biting force, which is, in turn, greatly influenced by the musculature, would offer resistance by virtue of the ability to maintain intercuspal position and interdigitation. The second major factor is the vertical or horizontal craniofacial pattern. Vertical growers lose anchorage faster than horizontal growers because they have less biting force.

Type of tooth movement

Anchorage varies with the type of tooth movement; whereby bodily movement requires more anchorage than tipping. The contemporary system of pre-adjusted appliances necessitates high demands of anchorage during the initial stages of the treatment, as the first few wires tend to unravel malocclusion according to the expression of bracket prescription, whereby tooth axis alignment, tip and crowding are unravelled simultaneously to bring the teeth in a position called ‘slot line up’.

Friction in the appliance system

Friction between wires and bracket slots adds to the resistance against tooth movement. Retraction force should first overcome the static friction at the bracket wire interface to initiate tooth movement and continue to overcome kinetic friction during tooth movement. So, to counteract frictional resistance, additional force is applied for anterior retraction, which can strain posterior anchorage.

Anchorage loss

The force involved in tooth movement follows Newton’s third law of motion, which states, ‘for every action, there is an equal and opposite reaction’. Tooth movement of the reactive member during orthodontic treatment is termed ‘anchorage loss’. It is undesirable in most instances.

1.
Mesial anchorage loss: Traditionally, anchorage concerns have been mainly against the mesial movement of the anchor teeth. Conventionally, anterior teeth are pulled using buccal segments as anchors. The unwanted mesial movement of the buccal teeth, termed ‘anchorage loss’, compromises the amount of retraction of the anterior teeth.
2.
Vertical and transverse anchorage loss: Earlier researchers and clinicians were concerned mainly with anchorage loss in an anteroposterior direction. However, the treatment outcome should also consider changes in vertical or transverse relationships, which can influence a tooth or a group of teeth at critical positions and, hence, the occlusal plane.

Most orthodontic biomechanics are extrusive and preventing this extrusion can be quite challenging specially in high angle cases. Extrusion of posterior teeth can result in unfavourable downward and backward rotation of the mandible, worsening the profile in high-angle and class II malocclusion.

Anchorage for fixed appliance

The control of anchorage in fixed dental appliances can be a complex process. Teeth are the primary source of anchorage. When a group of teeth needs to be moved, it can tax on the anchor teeth, especially during the retraction of the anterior segment against the buccal segment. However, several modalities can enhance anchorage. One option is to incorporate more teeth into the anchor unit. Another is to modify the biomechanics to support anchorage or to use ‘anchorage savers’. Although using extraoral anchorage with headgear is an option, it is hardly practised now. Instead, the use of mini screw implants (MSI) and SAS should be considered when appropriate, as they provide absolute control of anchorage.

Dental units

Teeth offer excellent anchorage; however, they are housed in a biodynamic environment suspended in the alveolar bone through the periodontal ligament (PDL), which reacts to force. The root surface area of the tooth determines its anchorage value. One may consider moving a tooth with a smaller root surface area against a tooth with a large root surface area, called an anchor tooth ( Fig. 54.4 ).

Differential force system : The experimental work by Storey and Smith confirmed that optimum force values differ based on the root surface area for each tooth. ^, Hence, if the incisors must be moved pitted against molars, a light force, which is optimum for the incisor movement, would be insufficient for the first molar with a greater root surface area. Therefore, a greater movement of the incisor would occur. Correspondingly, a higher force, which is optimum for the molar, is likely first to initiate movement of the molar before the incisors can move. Dr. P. R. Begg, in Adelaide, Australia, proposed the concept of differential force in the late 1930s, ^, and based on this philosophy, he developed the light wire technique.
Root surface area : A tooth’s anchorage value is a function of its root surface area, which is housed inside the alveolar bone. The greater the root surface area, the higher its anchorage value. Molars have a more extensive root surface area, with the upper first molar having the largest value. Canines come next in root surface area, followed by premolars and incisors, with the lowest value for the mandibular central incisor.
- The root surface area of a tooth is influenced by its root length, thickness, shape and the configuration of the number of roots it has.
- To avoid anchorage loss, the root surface area of anchor teeth should exceed the sum of the root surface area of teeth to be moved against anchorage units ( Fig. 54.5 ).
  
  Figure 54.5
  
  Root ratings have been calculated based on root surface area (cm ²) of each tooth.
  
  Multirooted teeth have large root surface areas, hence offer more resistance and need more force to move compared to teeth with smaller root surface area. The concept was introduced by Robert Lee of Australia and used by Roberts M. Ricketts in bioprogressive technique. Combined root surface areas of second premolar and first molar are close to that of three anterior teeth. Therefore, in maximum anchorage cases, additional/alternate anchorage conservation methods are utilised which include the use of second molar, anchorage savers such as TPA, headgear or mini screw for en masse retraction of anterior. In some situations, anterior retraction is performed in two stages, canine retraction followed by incisor retraction. Brian Lee suggested that for optimal tooth movement, a force of 200 g/cm ² of root surface is required. Ricketts, however, felt that their calculations on force values are higher and a reduction of 25% is required. Therefore, he suggested 150 g/cm ² as the optimum force value.
Developmental abnormalities of the root can increase or lower anchorage value. Developmental abnormalities of root form, such as dilaceration, increase the resistance to tooth movement, whereas developmental abnormalities resulting in short roots offer poor anchorage to their normal counterparts.
- An ankylosed tooth is an excellent anchor and a biological source of absolute anchorage. Intentional ankylosis is used in orthodontics to create an anchorage source; for example, deliberate ankylosis of the maxillary deciduous canines is performed to create an anchor for the protraction facemask.
Periodontal health : A relative equilibrium exists between the forces acting on a tooth and the periodontium’s biological resistance, maintaining the tooth’s position. Active stabilisation offers resistance due to metabolic effects in the PDL. Active stabilisation can overcome prolonged forces up to 5–10 g/cm ². Periodontal disease can reduce a tooth’s anchorage value by affecting PDL fibres in the presence of inflammation and reduced bone support.
Quantity and quality of alveolar bone : The volume and quality of osseous tissue that must be resorbed for a tooth to move a given distance indirectly represent resistance to orthodontic forces. Dense bone offers more resistance to resorption than spongy bone. The dense cortical bone is more resistant to resorption than the medullary bone. A mandibular alveolar process with a thick and dense bone offers greater anchorage than the maxilla.
Muscles as anchorage : The muscles of mastication offer resistance to anchorage loss through their biting force. In subjects with low mandibular plane angle or horizontal growers, the muscle attachment of the masseter is more vertical, and the temporalis heads are broad and more developed. The molars often resist moving mesially against forces in this situation compared to high-angle cases, where the muscles of mastication are less strong and biting forces are relatively lower.

Muscular forces, when redirected to favourable action on the teeth, such as for removable functional appliances and lip bumpers, serve as a source of anchorage. A lip bumper transmits the force of the hyperactive lower lip to the molars, thus aiding in their uprighting.

Types of anchorage

Reciprocal anchorage : Teeth may need to be pulled against each other to close spaces. For example, a midline diastema in the upper arch can be closed by tying them with a tight elastic thread, which is an example of reciprocal anchorage ( Figs 54.4 and 54.6 ). In orthodontics, we use reciprocal anchorage in the differential force system given by Dr. P. R. Begg, where when light forces are used to move teeth with small roots against molars, major movement occurs for incisors. If heavy forces are applied, molars will move first. The biological mechanism is described in the chapter on the biological basis of tooth movement ( Chapter 17 ).

Figure 54.6

Reciprocal anchorage.
Anchorage preparation : The principle of anchoring used in putting up a tent or anchoring a ship is applied in orthodontics to conserve anchorage and enhance the movement of teeth in the oral cavity. The anchor tooth is tilted distally, meaning the pulling forces are derived at 90 degrees to prevent anchor loss. This technique, commonly known as ‘anchorage preparation’, involves distal tilting of the anchor teeth to favourable angulations. Dr. Charles H. Tweed is credited with coining this term. You can learn more about this technique in Chapter 51 ( Fig. 54.7 ).

Figure 54.7

Fixed appliances derive anchorage from the teeth.

Anchorage source and anchorage preparation in fixed appliance. Tooth with larger root surface area offers greater anchorage. A group of teeth can be tied together to enhance anchorage. The second molar can be bonded to reinforce the anchorage. Tweed suggested anchorage preparation with the help of second-order or tip-back bends. Anchorage preparation in the lower arch involves the use of class III mechanics to prevent the root tips of buccal teeth from moving forward. After the introduction of built-in tip mechanisms in the pre-adjusted bracket systems, tip-back bends are rarely used. Molar stops and active omega loop enhance anchorage by preventing mesial movement of anchor tooth.
Stationary anchorage : A stationary anchorage is an anchor tooth or source that does not move against the forces of teeth to be pulled. The anchor tooth housed in a bioactive environment would show some movement and hence cannot be classified as a stationary anchorage in an absolute sense.
- In a real sense, only the extraoral source of anchorage derived from headgear would be a stationary anchorage. MSI and SAS also fall under this category.
Headgear : Very early in history, orthodontists realised the limitations of using teeth as an anchorage source, and thus, headgear was used to obtain extraoral anchorage. Headgears obtain support from the back of the neck cranial bones and can provide three-dimensional anchorage control depending upon the type of headgear and the direction of the force. Forces are transmitted from the headgear strap to teeth via the facebow or J hooks ( Fig. 54.8 ).

Figure 54.8

Extra oral stationary anchorage.

(A–C) Stationary anchorage from extraoral source is derived through headgear.

Source: Dept of Orthodontics, Faculty of Dentistry, University of Sydney, Australia.
Mini implants and skeletal anchorage systems : Temporary anchorage devices which include mini screw implants (MSI), skeletal anchorage system (SAS) and their variants have been integrated into the orthodontic arsenal. These devices provide an excellent source of anchorage. Chapter 72 , 73 discusses this aspect of orthodontic therapy.

Anchorage savers

A major part of the treatment planning and concern revolves around maintaining the anchorage in three dimensions of space.

Anchorage control during fixed appliance therapy necessitates biomechanical provision, including a distal tip of the anchor teeth, banding second molars, making a molar stop and retracting the anterior segment in two stages. The two-stage retraction of the anterior teeth was practised by Charles Tweed and followers of his philosophy of anchorage control. In two-stage space closure, the canines are retracted into extraction spaces first. On the completion of canine retraction, that is, its contact with the second premolar, the canine bracket in each buccal segment is tied to the second premolar and the first molar, reinforcing the existing anchorage. The incisor retraction is then completed using the enhanced anchorage. In this system, the treatment duration is increased, but the anchorage control is much better.

In addition, anchorage savers are incorporated. These include the following:

•
Transpalatal arch (TPA)
•
Translingual arch (TLA)
•
Nance palatal arch
•
Modified Nance arch
•
Vertical holding appliance (VHA)
•
Utility arch

Transpalatal arch : Robert A. Goshgarian introduced the TPA to the orthodontic armamentarium. It transversely spans across the palate between the upper first molars, with an omega loop in the midline. The TPA is effective as an anchorage maintenance device as well as an active orthodontic appliance if necessary to institute molar rotation ( Fig. 54.9 ).

Pocket Dentistry

Fastest Clinical Dentistry Insight Engine

Orthodontic treatment with the contemporary fixed appliance phase I: Laying the foundation, diagnostics and precise appliance placement

Introduction

First appointment and records

Designing a treatment plan and execution strategy